Table 3.

CYP1A1 hypomethylation mediated the effect of smoking and 1-OHP co-exposure on high 8-OHdG

Co-exposure	Total effect	Direct effect	Proportion mediated by CYP1A1 hypomethylation	P value
Smoking and1-OHP	1.03 (1.00–1.06)	1.02 (1.00–1.05)	13.6% (2.6–47.9%)	0.047

Covariates in the SAS macro include sex, age,years of working, drinking status, education and central heating

^aTotal effects of smoking and 1-OHP co-exposure on high 8-OHdGwere estimated without adjusting for CYP1A1hypomethylation

^bDirect effects of smoking and 1-OHP co-exposure on high 8-OHdG were estimated with adjusting for CYP1A1hypomethylation